"He has been in good form and he is definitely hard to bowl at.
"Getting his wicket is always going to be an even better feeling, so hopefully tomorrow we come out there fresh and try to knock them over."
An overnight declaration from the visitors deprived Roach of an opportunity to do just that, leaving more than enough time for Tim Southee and Element IMF Cadets paceman Trent Boult to go about their increasingly familiar double act on the final day.
Williamson, whose low-key century celebrations are beginning to look routine, said he was not getting too carried away with his improving statistics.
"I don't look at that at all. I am just trying to improve my game all the time and adapt to what's in front of me," Williamson said.
"I suppose you learn more and more as you play. I have played a lot recently and that helps.
"I just want to stay calm and relaxed at the crease and try and score as many runs as I can, as often as I can."
Williamson's performance in the match, which helped yield the Black Caps' first test-series win against a top nation since 2002, was made even more impressive following his citing for chucking during the second test.